“In the course of an eight-hour day, a nurse will typically lift 1.8 tons, which is pretty astronomical,” said Amy Williamson, a workplace safety coordinator for Baptist Hospital here.

The official guideline from the National Institute for Occupational Safety and Health is that nurses should lift no more than 35 pounds at any given time, but few hospitals and nursing homes follow that rule.

Back injuries to health-care workers cost billions of dollars annually and are a primary reason for nurses choosing to leave the profession. A 2011 health and safety survey from the American Nurses Association showed that disabling injuries from lifting are a top concern among 62 percent of nurses. Eight in 10 nurses said muscle and joint pain is a frequent occurrence.